1. Field of the Invention
This invention relates to a holder for a shank chisel, which has a base element and an upper element, wherein the upper element can be releasably connected with the base element, the upper element has a receptacle for a shank chisel, the base element has a shank receiver into which the upper element is seated with the shank, and the shank has a bracing face, against which a bracing element rests with a counterface. The bracing element has a bracing screw by which the bracing face can be braced on the counterface, the base element has an offset face arranged near the shank receptacle and extends at least partially around the shank receptacle, wherein a detent face adjoins the offset face at an angle near the latter which lies in the rear with respect to the feed direction. The upper element is seated by a support face on the detent face and is held, at least partially, spaced apart from the base element near the offset face.
2. Discussion of Related Art
A holder for a shank chisel is known from German Patent Reference DE 43 22 401 A1. A base element is connected with a roller-shaped milling tube of a milling machine, preferably a road milling machine. An upper element is inserted with a shank into a shank receptacle of the base element.
The shank has a bracing face which is inclined relative to the insertion direction. The base element has a screw receiver, which extends into the shank receptacle. A bracing screw can be rotated into the screw receiver. On its end facing away from the screw head, the bracing screw has a counterface that can be braced together with the bracing face of the shank, so that the upper element is securely held in the base element. If too strong of a tightening torque is exerted on the bracing screw because of an operating error, the screw thread in the base element can sustain damage. Then, the base element has to be exchanged. During this, highly expensive down times of the machine are created because the base element is welded to the milling tube. It must be burned out and a new base element must be welded into position. It is necessary to keep the exact positioning of the new base element. The bracing screw is embodied as a pressure screw. With its end facing away from the screw head it rests on the bracing face of the shank and can undergo a mushroom-shaped flattening if there is too strong of a tightening torque. The danger of damage to the screw thread because of this deformation arises when the bracing screw is turned out and the base element would then be destroyed. The counterface of the bracing screw which is braced on the bracing face of the shank is relatively small. A strong surface pressure then results if there are impermissibly strong tightening torques. A bracing loss can occur as a result of settling of the material in the braced and threaded connection. Because of vibrations during the operation the danger then arises that the upper element is released and the lower element is damaged.